Methods of signal transmission based on fiber optics, which are already widely used in long-distance communication, provide the advantages of broad bands and immunity to electromagnetic interference (EMI), and are thus being applied to high-capacity digital media transmissions, such as for high-definition digital video display devices, which require high-speed, high-density data transmissions.
In conventional methods of signal transmission based on fiber optics, however, the optical device for coupling the light-emitting elements with the optical fiber or for coupling the light emitted from the optical fiber with the light-receiving elements is not only very expensive but also quite difficult to use in performing optical alignment.
In particular, in a conventional method of optical alignment, the optical transmitter part is implemented by attaching light-emitting elements and light-receiving elements for sensing the optical outputs of the light-emitting elements, and by coupling a lens for collecting the optical signals from the light-emitting element. Then, the optical fiber is inserted, active optical alignment is performed with the optical fiber inserted, and the optical fiber is secured at an optimum position, to complete the optical alignment of the optical transmitter.
Active optical alignment refers to a method of optical alignment in which an electric current is applied to the light-emitting elements to emit optical signals, the optical signals thus emitted pass through the lens to produce an image at a particular distance, the optical fiber is aligned at this position, and, as the detected amount of optical signals entering the optical fiber varies according to the degree of alignment, the position is found at which the highest optical signal value is detected. This method is used in most alignment and packaging applications involving optical fibers and optical elements.
The optical receiver part includes aligning the optical fiber with the light-receiving element, and its assembly process is very similar to that of the optical transmitter part.
This method of active optical alignment, in which the light-emitting element or light-receiving element is driven directly and the degree of alignment with the optical fiber is sensed in real time to yield the optimum degree of alignment, requires a time-consuming manufacture process and expensive assembly apparatus.
Whereas the active optical alignment method involves manufacturing optical modules by laser welding while detecting optical outputs or optical currents in real time, the passive optical arrangement method is a method of alignment that does not require directly driving the optical elements and refers to technology for assembling based only on predetermined position information, to be highly beneficial in mass production.
An aspect of the present invention is to provide an optical device that includes optical modules of smaller and simpler structures and uses a minimal number of parts, so that the costs of the optical modules can be reduced, and the optical alignment can be performed passively for multiple channels in a simple manner.
Another aspect of the present invention is to provide a method of passively aligning the parts of an optical device that can minimize the alignment error, even when performing alignment for the light-emitting elements, light-receiving elements, lenses, and optical fibers of multiple channels using optical modules.